This brown Stereum or Peniophora-looking crust on Pine (found by Sally at Longshaw) took me some weeks to identify. I followed the instructions provided by Corticiacaea of Northern Europe (CNE) – the 7 volume most authoritative guide: “ First place a drop of KOH or your staining reagent on the slide”. I used KOH as my dried specimen was very hard and quite thick. After softening I added ammoniacal Congo Red. I was able to make a reasonable squash preparation, and could identify hyphae (dimitic – thin-walled generative and thick-walled straighter skeletal hyphae). Basidia were extremely hard to find, but basidioles with clamps were seen. The most striking feature were the smooth cystidia/hyphal ends protruding from the surface. Spores were not easy to find on the dried specimen, but as usual I had obtained a spore print before drying – the spores were Stereum-like ( hyaline, oblong-oval, approx 6-7 x 3, and amyloid).
From Fungi of Switzerland and CNE I got tentatively to Stereum, but as my specimen didn’t bleed red, and it didn’t look like any non-bleeding Stereum, and it also had clamps, I was at a loss.
I’ve been finding that sticking dried crust fungi straight into KOH , although helping to soften the material to be able to disperse the elements, can also destroy the cystidia. It can dissolve the beautiful crystalline covering of lamprocystidia and skeletocystidia which are crucial for some IDs.
I therefore made another section of the herbarium specimen in plain water – which showed the striking skeletocystidia of Amylostereum chailletii.
This specimen fits both the descriptions in CNE and FOS. (It is recorded on Pine in the UK as well as Spruce). At least it does for me. If I'm right then it's another first for Longshaw, and possibly for Derbyshire.
Steve

Field photo

Stereo microscope image

Cystidia after treatment with KOH and ammoniacal Congo Red - they are denuded of crystals